Best app for learning songs

[update for newest version: This app is literally unbelievable. I cant believe what they are able to do on an iPhone.]
Seriously. I cant believe they managed to make this app work on a phone. Literally impossible on the computers I worked with in college and now it lives on my phone. Welcome to the future.

I play along with songs at home on my iMac and then drop out the vocals on my phone and sing along while I drive. Awesome.

theRealSirshannon about Capo - Learn Music by Ear